Automatic ice makers run essentially continuously using two basic systems. These systems are the coolant recycle refrigerant system and the water/ice system. Fouling problems in the water/ice system occur which decrease efficiency and require down-time for maintenance and cleaning. The improvements in the ice making machines of this invention greatly curtail the necessity for downtime and or provide for cleaning and sterilization of the machine, which enhances the continuity and efficiency of operation of ice making machines.
THE COOLANT/REFRIGERANT SYSTEM
The coolant recycle refrigerant system is primarily composed of a compressor, a condenser, an expansion valve, an evaporator and interconnecting lines therefor. In addition this coolant/refrigerant system can also contain a reservoir for the refrigerant being used, a refrigerant drier, a hot gas solenoid valve to recycle hot gases through the evaporator after ice has been formed, thereby releasing the ice from the evaporator plate, and interconnecting lines therefor.
In operation, a coolant/refrigerant system contains an appropriate refrigerant, often including carbon dioxide or various halogenated hydrocarbons, particularly the fluorocarbons or fluoro, chlorocarbons, and begins operation during what is referred to as the freeze cycle. In the freeze cycle the compressor receives a vaporous refrigerant at low pressure and compresses it, thus increasing the temperature and pressure of this refrigerant. The compressor then supplies this high temperature, high pressure vaporous refrigerant to the condenser where the refrigerant condenses, changing from a vapor to a liquid, and in the process the refrigerant releases heat to the condenser environment. In large ice making systems the condenser may be located out of doors far away from the compressor operating within the confines of the ice maker machinery.
The liquid refrigerant is normally supplied from the condenser to the evaporator where the liquid refrigerant changes state to a vapor and, in the process of evaporating, absorbs latent heat from the surrounding environment. This cools the evaporator and any materials in close proximity or in contact with the evaporator. The refrigerant is converted from a liquid to a low pressure vaporous state and is returned to the compressor to begin the cycle again. During this so-called freeze cycle the evaporator plate, or ice tray or mold, of a typical ice maker, which mold is in contact with the evaporator or in close proximity thereto, is cooled to well below 0.degree. C., the freezing point of water. Often temperatures below -10.degree. C. or even temperatures of -25.degree. C. or below can be achieved.
During the freeze cycle the ice making mold of the typical ice maker has water contacted and pumped over it to build up the desired ice shapes, pieces, or forms.
THE WATER/ICE SYSTEM
The water/ice system primarily comprises at least a water supply, a water reservoir or water sump, means for discarding excess water from the circulating water system, such as a drain or overflow system, each sometimes equipped with a water dump solenoid valve, a water circulation or recirculation pump or other means for circulating water through the water/ice system, a water distributor, or means for distributing the circulated water across the ice-forming mold or evaporator plate, and an ice thickness sensing probe or means for detecting the thickness of the ice formed so as to terminate a freeze cycle and begin a harvest cycle. These water/ice systems may also contain a water curtain the purpose of which is to direct water flowing over the ice-forming mold or evaporator plate onto said plate or mold and collect and distribute unfrozen water into the water reservoir or sump. After the ice has been formed appropriately, the ice thickness sensing probe is activated, indicating complete formation of the ice sheet, pieces, cubes or shape desired. A harvest system is then initiated which stops the flow of coolant/refrigerant and begins an ice recovery process, such as, for example, beginning a hot gas recycle into the evaporator which heats the evaporator plate or ice forming mold thereby releasing the ice which falls into an ice collector reservoir.
ICE MAKING SYSTEMS
The above described ice making systems, including systems having a harvest cycle refrigerant control system basically described above, are additionally described in U.S. Pat. No. 4,907,422 and U.S. Pat. No. 4,878,361. In general, these systems provide for ice making machines operating at relatively low temperatures, i.e., below 50.degree. F. ambient, having head pressure control valves provided in part to maintain a minimum head pressure to insure that compressor heat will be available for the next ice harvest cycle, and said valve generally being designed to prevent back up of liquid refrigerant into the condenser during cold temperatures.
During the harvest cycle the vaporous refrigerant is supplied to the evaporator through a hot gas valve contained in the coolant/refrigerant system. The valve typically has a fixed orifice acting as a metering device. This normally functions satisfactorily in self-contained systems with relatively small refrigerant charges, providing acceptable harvest times without returning unacceptable amounts of liquid refrigerant to the compressor.
In systems having large refrigerant charges, the discharge pressure during a harvest cycle tends to be higher at elevated ambient outdoor temperatures. As a result, more refrigerant may flow through the fixed orifice in the hot gas valve and into the cold evaporator where it condenses. If this condensed refrigerant reaches the compressor, it can damage this compressor and greatly affect the efficiency of the operation of the compressor. Therefore, as taught in the patents cited above, the system normally controls the amount of refrigerant circulated between the compressor and the evaporator during the harvest cycle. The amount of refrigerant varies from system to system depending upon operating conditions, such as the size of the evaporator.
The amount of refrigerant can be monitored, for example, by the compressor's suction pressure, and additional refrigerant from the condenser is added as needed. Ice making systems such as those described in U.S. Pat. No. 4,907,422 and U.S. Pat. No. 4,878,361, as well as ice making machines taught in U.S. Pat. No. 4,898,002 and U.S. Pat. No. 4,845,955, may be further enhanced by improvements such as a drain valve control as taught in U.S. Pat. No. 4,785,641 and a particular advantageous pump assembly as taught in U.S. Pat. No. 4,767,286. Improvements for harvest pressure regulator valve systems, as taught in U.S. Pat. No. 4,774,815, may further be improved with anti-blocking controls as taught in U.S. Pat. No. 4,550,572.
Also, ice cube making machines having vertical, open faced freezing molds over which water is circulated from an underlying trough or sump to build up ice, as taught in U.S. Pat. No. 4,489,567, can be incorporated as the evaporator plate mentioned above. Likewise harvest controls such as those controls taught in U.S. Pat. No. 4,480,441, may also be incorporated into the ice making machines of this invention. In addition, the evaporator and ice molds may be formed of integral, extruded aluminum parts, as taught in U.S. Pat. No. 5,193,357.
All of the U.S. Patents and applications cited above are incorporated herein by reference.
THE PROBLEM OF LONG TERM OPERATION
Even after all of the improvements in ice making machines brought about by the careful design set forth in the above cited and incorporated patents, problems still exist which can impede the operation of an ice making machine, particularly an ice making machine running automatically and for extended periods of time. These problems include the fact that during extended use, the water/ice system has a tendency to accumulate soils, dirts, dusts and water hardness components, such as calcium carbonate and magnesium salts, onto the surfaces of the water/ice system. Occasionally, depending upon the environment in which the ice making machine is located and the quality of the waters supplied to the ice making machine, various biological deposits can form, including microbiological growths, yeast residues and slimes.
When these dusts, soils, water hardness deposits and microbiological growths, yeast residues and slimes form on the water/ice system surfaces, they can impede the flow of water through the system and can cause decreased heat transfer efficiency, particularly on the evaporator plates and ice forming molds on which ice is being made. When this happens, these water/ice system surfaces have to be cleaned to maintain proper ice making operations. This cleaning process normally requires dismantling that portion of the ice making machine containing these surfaces and washing and scrubbing the surfaces using acidic cleaner solutions. After this washing and scrubbing has been completed, much care must be taken to rinse the cleaning solution from the surfaces to avoid contact with ice later formed from these surfaces. Then the machine must be reconstructed. This is labor intensive, costly and inefficient.
In addition, problems still can occur even when machines are cleaned without disassembly by injecting acid solution into circulating waters and manually turning off the coolant/refrigerant system. When the fouled surfaces are washed with the cleaners, particularly when the cleaner is acidic, extended contact time with the metal surfaces and these acid cleaners can eat away and destroy, or most assuredly shorten the effective life of, these metal surfaces, and coatings thereon, such as the evaporator plate. These metal surfaces are primarily designed with alloys or metal plating that contain metals that conduct heat easily, such metals including but not limited to aluminum, copper, brass, irons and steels, and the like, all of which tend to corrode on contact with acid based cleaners. Also, cleaner residue can cause the ice formed immediately after such manual cleaning to be of poor quality.